This application is based upon Japanese Patent Application No. 2000-224088 filed on Jul. 25, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
This invention relates to a semiconductor device having a heat protection circuit.
2. Description of the Related Art
Recently, a semiconductor device having heat protection circuits has been proposed. In such a kind of the semiconductor device, an output transistor, as an output portion, is provided to apply current to a load such as a motor, coil or the like connected thereto. The heat protection circuit detects heat emitted from the output transistor through a semiconductor substrate in which the output transistor is formed.
Commonly, the heat protection circuit has a diode formed near the output transistor and a control circuit. The heat protection circuit detects the heat by detecting change in voltage of the diode.
When the heat protection circuit detects high temperature which may be caused by overcurrent flowing the output transistor and may break the output transistor soon, the heat protection circuit turns off the output transistor compulsorily to prevent the output transistor from being broken.
Lately, such the semiconductor device is required to have plural output portions each having an output transistor in a common semiconductor substrate. Each output portion drives a different load. Therefore, some of the output portions may drive their own loads at the same time. Moreover, a heat protection circuit may be provided in each output portion. In this situation, when a heat protection circuit in the predetermined output portion detects heat emitted and transmitted from a neighboring output portion, this protection circuit turn off the predetermined output portion that is to be protected by this protection circuit, even if the predetermined output portion does not emit heat that is higher than a predetermined level to turn off the predetermined output portion.
This invention has been conceived in view of the background as described above and an object of the invention is to provide a semiconductor device having heat protection circuits capable of protection of each output portion precisely.
According to a first aspect of the present invention, a semiconductor device has plurality of output portions and plurality of heat protection circuits each of which protects each of the output portions. In other words, a plurality of pairs having an output portion and a protection circuit are formed in a semiconductor substrate. Moreover, each pair of the output portion and the protection circuit is thermally isolated from each other by a heat transmission restraining portion formed between each of the pairs of the output portion and the heat protection circuit.
Preferably, the heat transmitting restrained portion is an insulation film.
Preferably, the output portion has a first electrode pad and a second electrode pad, and the heat protection circuit is formed adjacent to one of the first electrode pad and the second electrode pad since the one of them may emit heat most.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings.